Project Summary: We have shown previously that we can produce cells that share many of the characteristics of hepatocytes from human pluripotent stem cells. The process closely mirrors that which occurs during liver development in mammals. The differentiation of the cells is synchronous, reproducible, and efficient and could provide a basis for the discovery of novel pathways that regulate the formation of human hepatocytes. We therefore propose to use this cellular differentiation system as a platform to screen for small molecules that can impact the formation of hepatic progenitors. We believe that success in the proposal will uncover cellular processes and molecular pathways that contribute to the formation of hepatocytes from human pluripotent stem cells in culture. Such findings will aid in the rational design of protocols that can produce clinically relevant hepatocytes for the study and treatment of hepatic disease as well as provide new mechanistic insight into development of the liver.